Undersized Lifesteal Crossbow (5e Equipment)
From D&D Wiki
Weapon (Crossbow, light), Very Rare (requires attnement)
This crossbow saps the life of your enemies and bolsters your life force.
When you attack a creature with this crossbow and roll a 20 on the attack roll, that target takes an extra 10 necrotic damage if it isn't a construct or an undead. You also gain 10 temporary hit points.